TNM staging and grading for maxillary sinus cancer

The stage of a cancer tells you how big it is and how far it has spread. It helps your doctor decide the best treatment for you.

TNM system stands for Tumour, Node and Metastasis. It is the most common way to stage nasal and paranasal sinus cancer. Doctors may also use the number system.

Tumour (T)

Tumour describes the size of the tumour (area of cancer).

Tis (carcinoma in situ) means the tumour is in the top layer of cells that line the inside of the maxillary sinus and has not grown deeper.

T1 means the tumour has grown deeper, but is only in the tissue lining the sinus (mucosa). It has not grown into the bone.

T2 means the tumour has begun to grow into the bone surrounding the maxillary sinus, but not into the bone of the back part of the sinus.

T3 means the tumour has grown into the back (posterior) wall, or into the ethmoid sinus, the tissues under the skin, or the bottom or side of the eye socket.

T4 is split into two groups:

T4a means the tumour has grown into the:

• skin of the cheek
• front part of the eye socket
• bone that separates the nose from the brain (cribriform plate)
• sphenoid sinus
• frontal sinus, or bones (pterygoid plates) or other parts (infratemporal fossa) in the face

This is also known as moderately advanced local disease

T4b means the tumour has grown into the:

• area connecting the back of the nose to the back of the mouth (nasopharynx)
• back part of the eye socket
• brain
• layer of tissue covering the brain (dura)
• some parts of the base of the skull, or certain nerves that connect the brain to the body (cranial nerves)

This is also known as very advanced local disease.

Node (N)

Node (N) describes whether the cancer has spread to the lymph nodes.

N0 means there is no cancer cells in nearby lymph nodes.

N1 means there are cancer cells in one lymph node on the same side of the neck as the tumour, but the node measures 3cm across or less.

N2 is split into 3 groups based on how many lymph nodes are affeceted, their size and if they are on the same side or both sides of the neck:

• N2a means there are cancer cells in one lymph node, on the same side of the neck, that is more than 3cm across but no more than 6cm.
• N2b means there are cancer cells in more than one lymph node on the same side of the neck, but none of them are more than 6cm across.
• N2c means there are cancer cells in at least one lymph node on the other side of the neck (or on both sides), but none are more than 6cm across.

N3 is split into 2 groups based on the size of the lymph node and whether it has spread outside the lymphnode:

• N3a means that the cancer has spread to at least one lymph node that is larger than 6 cm across.
• N3b means it has spread to a lymph node and has grown outside of the lymph node.

Metastasis (M)

Metastasis (M) describes whether the cancer has spread to a different part of the body.

M0 means the cancer has not spread to other parts of the body.

M1 means the cancer has spread to other parts of the body, such as the lungs, brain, bone or liver.

Together, the T, N and M stages give a complete description of the stage of your cancer. For example, if you have a T2, N0, M0 cancer of the maxillary sinuses, you have a tumour that has begun to grow into the bone of the maxillary sinus. The lymph nodes are clear and there is no spread of your cancer to other parts of the body.

Grading

The grade of a cancer tells you how much the cancer cells look like normal cells. There are 3 grades of maxillary sinus cancer:

• grade 1 (low grade) - the cancer cells look very much like the normal maxillary sinus cells
• grade 2 (intermediate grade) - the cancer cells look slightly like normal maxillary sinus cells
• grade 3 (high grade) - the cancer cells look very abnormal and very little like normal maxillary sinus cells

The word differentiation means how developed or mature a cell is. So you may hear your doctor describe grade 1 cancer cells as well differentiated. Grade 2 cancer cells are moderately differentiated. Grade 3 cancer cells are poorly differentiated.

The grade of the cancer gives your specialist a guide as to how the cancer is likely to behave. Low grade cancers are usually slower growing and less likely to spread.

High grade cancers are likely to be faster growing and are more likely to spread. This is only a guide. Your specialist will consider all your test results, and the stage of the cancer (see above) when deciding which treatment is best for you.